Fragment receiving and transmitting is a common method for enhancing transmission reliability in radio transmission. Generally speaking, the fragment receiving and transmitting refers to a method that a transmitter divides a complete MAC layer data frame or command frame into multiple small data packets (also known as fragments), and a receiver receives and combines these small data packets into the original data frame or command frame.
Usually, the transmitter transmits the data frame or command frame to the receiver after dividing it into fragments. The transmitter suspends transmitting and waits for an acknowledgement message after transmitting each group of fragments. The receiver transmits, after receiving each group of fragments, an acknowledgement message including a receiving state of each fragment in the group of fragments to the transmitter. The transmitter transmits, after receiving the acknowledgement message of the group of fragments, next group of fragments. Information of the fragments, which are not correctly received, in the group of fragments may be preferentially included in the next group of fragments.
The receiver needs to compete for a channel when transmitting the acknowledgement message including the receiving state of each fragment in the group of fragments. To be specific, the channel may be competed and occupied by other nodes during a period from the transmitter completely transmitting the last fragment of each group to the receiver preparing to transmit the acknowledgement message; therefore, the acknowledgement message cannot be transmitted in time, thus an entire fragment receiving and transmitting process is delayed.